Process and installation for the production of refrigeration thru high-pressure gas



Jan. 21, 1964 M. SEIDEL ,7

PROCESS AND INSTALLATION FOR THE PRGDUCTION 0F REFRIGERATION mu HIGH-PRESSURE GAS Filed July 13, 1960 2 Sheets-Sheet 1 Jan. 21, 1964 I M. SEIDEL 3,118,751

PROCESS AND INSTALLATION FOR THE PRODUCTION OF REFRIGERATION mu HIGH-PRESSURE GAS 2 Sheets-Sheet 2 Filed July 13, 1960 llite States Patent PROESS AND INSTALLATZGFJ FOR THE PRODUC- TEGN Gi REFPEGEPATIQN THRU HIGH-PRES- SURE GAS lvlax Seidel, Munich-Salim Germany, assignor to Gesellsehaft iiir Lindes Eisrnaschinen Aktiengesellschatt, Hoiiriegelslrreuth, near Munich, Gennany Filed duly 13, 196i Ser. No. 42,622 Claims priority, application Germany July 29, 1959 14 Claims. (Cl. 62-9) This invention is concerned with the provision of a process of and an apparatus for producing refrigeration through high-pressure gas of above-critical pressure with cooling through work-performing expansion for meeting the requirements in the liquefaction-or in the separation into its components-of the gas. The expressions critical temperature and critical pressure as used herein are intended to have the meanings given for them in Handbook of Chemistry and Physics, 42nd ed., 1960/ 61, page 3682.

It is known, according to the process of Heylandt, that high-pressure gases of, for example, 200 atmospheres gauge pressure can be cooled by work-performing expansion, the cooling thereby obtained being transmittedafter an interposed separation of the gas in some cases-to another part of the high-pressure gas and the latter liquefied by throttling. In this process, a very large pressure drop takes place in the expansion machine, for which reason piston machines must generally be employed. During the work-performing expansion the gas is cooled to such an extent that its temperature lies only a little above the liquefaction limit.

An object of the present invention is to restrict the work-performing expansion to a partial pressure drop in the below-critical pressure range, but to carry out the process at relatively highly elevated temperature, preferably in the above-critical temperature range. The first criterion makes it possible to have the work-performing expansion for large gas volume take place with particularly high thermal efficiency: the latter criterion utflizes the fact that the refrigerating capacity, for equal pressure drop, is the greater the higher is the mean working tem perature of the expansion.

In the predominantly above-critical pressure range the invention utilizes only the Joule-Thomson cooling elfect for the refrigeration; in the range of below-critical pressures, however, there is additionally utilized the very good refrigerating capacity of a Work-performing expansion at high mean working temperature. The cold produced at :1 high Working temperature through work-performing expansion is, then, transformed to the much lower required temperature through the total high-pressure air, and therefore, not only through the non-work-performing expanding part according to the principle of the vaporization refrigeration machine.

Accordingly, the invention concerns the production of refrigeration by high-pressure gas of above-critical pressure with cooling through work-performing expansion for the coverage of the cooling losses in the liquefaction of the gas, or in the separation of the gas, for obtaining liquefied gases and/ or, in a given case, for obtaining liquid gas separation productsin particular, of air separation productsand is thereby characterized in that the highpressure gas or" above-critical pressure of preferably 100 to 300 kg./crn. cooled by means of the expanded gas or expanded gas separation products, is throttled to belowcritical pressure of preferably to kg/cmP, separated from the liquefied part in the heat-exchange with the high-pressure gas or considerably warmed with a part of the same, cooled through work-performing expansion and then, in some cases with an interposed gas separation in the heat exchange with the high-pressure gas or a part of the same, again heated to room temperature.

This has the advantage first of all that in the Workperforming expansion at small pressure drop and high mean working temperature a higher thermal efficiency can be attained than at higher pressure drop. The greater expansion volume as compared with the expansion with large pressure drop makes it possible to build large ma chine units since turbines-which do not permit any lubricant to enter the expanded gas-are less susceptible to disturbances, and entail smaller installation costs, than do reciprocat ng expansion machines.

In spite of the decreased pressure drop the work-performing expansion, on account of the higher mean working temperature, does not give a smaller cooling effect than does the high-pressure expansion over the entire highpressure drop. t the sarne time, the simpler construcchines designed as turbines are accompanied by an at tion and smaller space requirement for the expansion machines designed as turbines are accompanied by an at least equal refrigeration capacity of the high-pressure expansion.

in applying the process according to the invention for a high-pressure cycle incorporated with a gas separation installation the expansion turbine, in a special design form with closed cycle, is operated with the total cycle quantity, in comparison wtih the familiar processes with high pressure expansion machines which have available only about 60 percent of the gas for the work-performing expansion.

The refrigeration is in this case produced through indirect herit-exchange, transmitted to a special dry-condensed cycle gas, and through the latter supplied to the separation apparatus so that not even traces of oil from the compressors for compressing the high-pressure cycle gas can reach the separation apparatus.

In the process according to the invention lt'gh-pressure gas of above-critical pressure, preferably between to 380 leg/ch1 is s pplied to a first heat-exchanger in which the gas is cooled through heat-exchange with cold gas coming from the expansion turbine. The high-pressure gas is then divided into two partial streams each of which is further cooled by an additional heat-exchange One of the streams is cooled by the gas coming from the expansion turbine, the other by the gas going to the turbine. After traversing these heat-exchan ers the two partial gas streams, either separated or combined, pass through a heat-exchanger in which they are further cooled by the gas flowing back from the expansion vessel to the turbine. The two separated partial strems are then expanded into an expansion vessel to below critical pressure, preferably between 10 and 30 l g./cm. whereby a part of the gas is liquefied. The liquefied part can be removed While the remaining gaseous part flows bacl; through the heatexchanger connected ahead or" the expansion turbine, is thereby heated, and is then expanded in the expansion turbine. After expansion, the gas flows back through the heat-exchanger and is heated by the arriving high-pressure gas. The high-pressure gas, already compressed and dry, is supplied from the outside to the first heat-exchanger of the installation. It is of advantage to employ a gas cycle where the back flowing gas is compressed by a compressor and where the quantity drawn off as L quid, through the supply of fresh gas before, during or after the compression, in the warm portion, is, after the work-pretorming expansion, replaced by gas coming from the low-temperature part of a gas separation apparatus in the cold part of the cycle.

If the process described thus far is used in connection with a familiar gas separation apparatusfor example, one which uses regenerators for the heat-exchangethe a expansion vessel in which the liquefied high-p'essure gas collects can communicate with the separation column. By transferring an equivalent quantity from the lowtemperature part of the gas separation apparatus under separation pressure back to the cold part after the workperforrning expansion, the pressure behind the expansion machine will be held constant at the pressure of the separation column. From the pressure-column a twocolumn rectifictaion installation, for example, the low boiling gaseous end product can be removed and with it the cycle operated or replenished.

The liquid expanded in the separation apparatus can be undercooled by the gas supplementing the cycle or by the gas separaiton product before this supplementing gas is itself supplied to the cycle. it is also possible to heat the supplementing gas for the cycle the indirect heatexchan er with the gas to be sepai .ted, in particular, through pipe coils which are embedded in the main heatexchangers of the gas separation apparatus, preferably in the storage mass of regenerators, and to supply it to the cycle in the heated state before the compression.

The gas liquefied in the expansion vessel can also be again vaporized through in irect heat-exchange with another gas. The total cycle gas is thenravailable for the work-performing expansion. Thereby this other gas can be liquefied. In this cas the total expanded high-pressure gas of the installation can be repeatedly compressed and expanded in the closed cycle.

This second gas can be compressed to a pressure at which it is itself liquefied through evaporation of the liquefied part of the throttled high-pressure gas. In this process the second gas to be liquefied can be precooled (entirely, or in part) in the heat-exchange with the cycle gas to be heated or with a part of it.

It is, furthermore, possible to take high-boiling point gas from a gas separation installation and to compress it, preferably dry and free of oil, to a pressure such that it vaporizes the liquefied cycle gas in the indirect heatexcaange and is itself liquefied in the process. The liquefied gas is then expanded into the separation apparatus. The expansion pressure of the work-performing expansion of the cycle can thereby be held at constant pressure through communication with suitable parts of the separation apparatus under constant pressure.

Therliquefied high-boiling point gas in indirect heatexchange with the liquefied cycle gas to be vaporized can, before its compression, be totally or partially heated through indirect heat-exchange by pipe coils inserted in the main heat-exchangers of the gas separation apparatusin the case of regenerators, in the storage mas while a part of the high-boiling point gas can be heated in indirect heat-exchance with itself before the compression. If occasion arises, the compression of the high-boiling point gas can tale place in common with the compression of the high-boilins point gas intended for consumption, preferably dry and free of oil.

To maintain the temperature equilibrium in the regenerators, a portion of the work-performing expanded cold cycle gas, that is regulateable by hand or automatically, can be conducted through the pi e coils in the regenerators and again be supplied to the warm part of the cycle. The gas quantity to be warmed in the pipe coils in the regenerators can also be cooled to the separation temperature by the expansion temperature of the work-performing expansion before the -eating in the pipe coils or, without preliminary further cooling, only be conducted in the warmer part of pipe coils in the regenerators.

In the application of the process in air separation installations the expansion machines are preferably operated with air or nitrogen, preferably between 25) to 35 atmospheres and about atmospheres, and for the possible evaporation of the liquefied cycle gas oxygen preferably is used which desirably is compressed to l5 to 30 pressed in the compressor to above-critical pressure and is supplied to the first heat-exchanger 2 through the pipe ii. in the heat-exchanger the gas is cooled by counterfiowing cold gas. The gas stream is then divided at 13, one part passing th ough the heat-exchanger 4 and there being cooled by the cold gas coming from the turbine 35 over pipe 1d, while the other part of the gas stream is cooled in the heat-exchanger 5 by the gas fl wing to the turbine. The two gas streams, separated in the pipes 15 and K7, are then led to a heat-exchanger 6 Where they further cooled through the non-liquefied portion of the gas flowing back through the pipe 19. The separated streams are then expanded through the valves 7 and in the expansion essel 9 to below critical pressure. Thereby a part of the gas is liquefied and collects in vessel 9, while the non-liquefied part is conducted to the expansion turbine through pipe 15 heat-exchanger 6, pipe 18, heat-exchanger 5 and pipe lie". A pipe 24 conducts the expanded gas to heat-exchanger 4 from which it goes to the heat-exchanger 2 and from there, by way of pipe 12, again to the compressor 1. The gas condensed as liquid can be replaced by dry low-pressure gas through pipe 22 and valve 23, or by dry high-pressure gas through a pipe 2:. shown in dotted line. it is also possible to omit the compressor entirely and to conduct the high-pressure gas by way of pipe 21 from the outside of the installation. The liquid accumulated in the expansion vessel 9 can be drawn off by the valve 1 3 through pipe 20.

FIG. 2 shows an installation in which the condensed high-pressure gas is vaporized through indirect heatexchange with a condensing auxiliary gas. This gas is supplied to the apparatus through the pipe 2d. A part flows through pipe 26 and the heat-exchanger 29 into the pipe coils 31 in the expansion vessel 9, while another part of the supplied gas is supplied by way of pipe to the heat-exchanger 27, then to heat-exchanger 28 and by way of pipe 39 likewise to the pipe coils 31. The gas is then expanded through a valve 32 into a vessel 34. Here the condensed gas is accumulated and can be drained oil through a valve 33. The non-condensed part flows through pipe 35 to the heat-exchanger 29 and leaves the apparatus at 36.

PEG. 3 shows an installation in which the process according to the invention can be applied to the production of refrigeration for a gas separating installation. Of the low temperature gas separation installation only a two-stage rectifying column 39, 49 is schematically rep resented in which all parts non-essential for the process according to the invention have been omitted; namely, the pipes to ad from the column as well as the pipes and valves for the wash liquids are not represented. There are also omitted the principal heat-exchangers, for example, regenerators, for the entering or leaving gas. As cycle gas, low-boiling point gas is taken in the gaseous form from pressure column 39 through a pipe 41 and supplied to t e heat-exchanger 4 by Way of an undercooled counterflow heat-exchanger 47. From heat-exchanger 4 it passes through heat-exchanger 2 and pipe 12 to the compressor 1. In the manner already described, a part of the gas is liquefied by expansion into the expansion vessel 9. The liquid in pipe 37 is conducted through the undercooling heat-exchanger d7, expanded through the nozzle 38 and again supplied to the lower column of the two-column rectifier 39.

FIG. 4 shows an installation in which hi h-boiling point gas is liquefied in a' cycle separated from the expansion cycle. The high-boiling point gas is taken from the column 40 through pipe 42 and conducted through the pipe coils 49, which are inserted in regenerators not here indicated, to the compressor 43. Here the gas is compressed to the pressure at which it condenses in heatexchange with the liquid to be vaporized in the expansion vessel. It is conducted to through pipe 45 to a heatexchanger 27 and then to a heat-exchanger 28 before it is liquefied in pipe coils 31. It is then conducted through pipe 46 to the heat-exchanger .7 and, with the aid of valve 48, expanded into the upper column 4t). Compressed, high-boiling point gas can be taken from the installation through the valve 44. Moreover, for suitable refrigeration capacity, liquid products can be taken from the gas separation installation, for example, liquid highboiling point material through the pipe 50.

I claim:

1. In a process for the production of cold by throttleing and work-performing expansion of a gas, the method which comprises cooling a gas which has been compressed (1) to above critical pressure at ambient temperature in a first cooling stage (2), dividing said compressed and cooled gas (13) into a first stream (16) and a second stream (17), cooling said first and said second streams in a second coolin stage (4, 5) and in a following third cooling stage (6), throttling said first and said second streams separately (7, 8) to below-critical pressure thereby liquefying them at least partially, separating a gaseous part from a liquid part (9), withdrawing the gaseous part (19), heating it by heat-exchange with the first and the second streams in the third cooling stage (6), heating it further by heat-exchange with the second stream in the second cooling stage (5), expanding it by work-performing expansion (3), heating said expanded gas by heat-exchange with the first stream in the second cooling stage (4), and then heating it in said first cooling stage (2) by heat-exchange in the compressed gas to ambient temperature.

2. Process according to claim 1, in which the compressed gas after expansion and warming to ambient temperature is compressed and expanded again in a cycle.

3. Process as claimed in claim 1, in which the separated liquefied part from the process is withdrawn and replaced by cold dry gas before said first cooling stage.

4. Process according to claim 1, in which the separated liquid part is withdrawn from the process and is replaced by compressed gas of ambient temperature before said first cooling stage.

5. Process according to claim 1, in which the separated liquid part is evaporated by heat-exchange with a condensing gas (31) and the gas being formed by said evaporation is processed together (l?) with the gaseous part remaining after throttling the compressed cooled gas.

6. In a process for the production of cold in a low temperature gas separation plant comprising a rectifying device, the method which comprises withdrawing a part of a separation product in gaseous form from the rectifying device, warming it to ambient temperature in countercurrent with a warm gas to be cooled, compressing it to above-critical pressure, cooling it by heat-exchange with the gaseous separation product withdrawn from the rectifying device, throttling it to a beloy -critical pressure thereby liquefying part of it, separating gaseous part from liquid part, heating the gaseous part by heat-exchange with the compressed separation product, expanding it by work-performing expansion and heating it together with the separation product withdrawn from the rectifying device, and feeding the liquid part, obtained by throttling, into the rectifying device.

7. In a process for the production of cold in a low temperature gas separation plant comprising a rectifying device, the method which comprises withdrawing a part of the low boiling component in gaseous form (41) from the rectifying device (3?) Warming it by heat-exchange in a fourth cooling stage (47) heating it further by heatexchange in a second (4) and in a first (2) cooling stage, compressing it to above-critical pressure (1) and cooling it in countercurrent with itself in said first cooling stage (2), dividiru the compressed and cooled gas (13) into a first stream (16) and a second stream (17), cooling said first and said second streams in the second cooling stage (4, 5) and in a following third cooling stage (6), throttling said first and said second streams separately (7, 8) to below critical pressure thereby liquefying them at least partially, separating a gaseous part from a liquid part in a separator (9), withdrawing the gaseous part (id), heatin it by heat-exchange with the first and the second streams in the third cooling stage (6), heating it further by heat-exchange with the second stream in the second cooling stage (5), expanding it by work-performing expansion (3), heating the expanded gas by heat-exchange with the first stream in the second cooling stage l) together with the gas withdrawn from the rectifying device (39) in the second (4) and the first (2) cooling stage to ambient temperature, withdrawing the liquid part (37) from said separator (9) cooling it in heatexchange in said fourth cooling stage (47), throttling it (38) and feeding it into said rectifying device (39).

8. Process as claimed in claim 7, in which the gas to be separated is air, and'in which the low boiling component withdrawn from the rectifying device is nitrogen and this nitrogen is compressed to an above-critical pressure of from about 100 to about 300 lag/cm. and throttled to a below-critical pressure of from about 10 to about kg/cnm 9. In a process for the production of cold in a low temperature gas separation plant which comprises a refrigerating cycle according to claim 5, and which comprises further withdrawing part of a gas separation product from the rectifying device, heating it to ambient temperature (49), compressing (43) it, withdrawing (44) part of it from the gas separation plant and cooling (27, 23, 31) the remaining part by heat-exchange with gas of the refrigerating cycle, condensing it by heat-exchange with evaporating liquid obtained by throttling the compressed gas of the refrigerating cycle, and feeding the condensed gas into the rectifying device.

10. In a process for the production of cold in low temperature gas separation plant comprising a rectifying device the process which comprises withdrawing part of the high boiling component from the rectifying device (4) in gaseous form, warn-ling it to ambient temperature (49), compressing it (43.), cooling it by heat-exchange (27, 2'8) with gas of a refrigerating cycle, condensing it by heat-exchange (31) with a liquid contained in a separator (h) and feeding it as back into the rectifying device Withdrawing (41) part of the low boiling from the rectifying device (3%) component for compensating losses of the gas of the refrigerating cycle, warming it in a second cooling stage (4, 5) heating it further in a first cooling stage (2.) in countercurrent with itself, compressing it to above-critical pressure (1), cooling it in said first cooling stage (2), dividing the compressed and cooled gas (13) in a first stream (16) and a second stream (17), cooling said first and said second stream in the second cooling stage (4, 5) and in a following third cooling stage (6), throttling said first and said second stream separately (7, 8) to below-critical pressure thereby liquefying them at least partially, separating a gaseous part from a liquid part in said separator (9) with drawing the gaseous part (19), heating it by heat-exchange with the first and the second stream in the third cooling stage (6), heating it further by heat-exchange (28) with the high boiling component to be liquefied then by heat-exchange with the second stream in the second cooling stage (5), expanding it by work-performing expansion (3), heating the expanded gas by heat-exchange with the first stream irr the second cooling stage (4) together with the gas withdrawn from rectifying de- '7 vice (41) in the second (4) and the first (2) cooling stage to ambient temperature.

11. Apparatus for production of cold a gas liquefaction plant or in a plant for gas separation by workpertorn'iing expansion, in which the output of a compressor is connected to the Warm end of one flow path of a first heat-exchanger, the cold end of which latter is connected to one flow path of a second heat-exchanger and one flow path of a third heat-exchanger the cold ends of the second and third heat-exchangers are connected to the Warm ends of two flow paths in a fourth heat-exchanger, and the cold ends or" said two iiow paths are connected by valve-equipped connections with the medium part of a vessel; connecting means from the head of said vessel to the cold end of a third flow path of the fourth heat-exchanger, connecting means from th warm end of said fourth heat-exchanger to the col end of a second flow path of the third heat-exchanger, means connecting the warm end of said second flow path of said third heat-exchanger to the input of an expansion machine, means connecting the output of said expansion machine to the cold end of the second flow path of said secondheat-enchanger, and means connecting the warm end of said second heat-exchanger to the cold end of the first heat-exchanger, and means connecting the warm end of the first heat-exchanger to the input of said compressor.

12. Apparatus as defined in claim 11, in which there are provided heat-exchanging means, in particular pipe coils, in the lower part of said vessel for liquefy-ing a gas in said heat-excl1anging means.

13. Apparatus as defined in claim 11, in which the bottom of said vessel is connected by heat-exchanging and expansion means with a rectifying column.

14. Apparatus as defined in claim 13, in which the Warm end of one flow path of said heat-exchanging means is connected with the rectifying column, and the cold end of which is connected with the cold end of said second flow path of said second heat-exchanger.

References Cited in the tile of this patent UNITED STATES PATENTS V 1,992,486 Hunt Feb. 26,

2,494,120 Ferro Jan. 10, 1950 2,557,171 Bodle June 19, 1951 2,583,090 Cost Ian. 22, 1952 2,585,288 Van Nuys Feb. 12, 1952 2,629,239 Gantt Feb. 24, 1953 2,700,282 Roberts Ian. 25, 1955 2,785,548 Becker Mar. 19, 1957 2,850,880 Iakob Sept. 9, 1958 2,932,173 Mordhorst Apr. 12, 196i) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIGN Patent N0 $118,751 January 21, 1964 Max Seidel It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 37, for "in" read with "-"n,

Signed and sealed this 16th day of June 1964,

(SEAL) Attest:

ERNEST W; SWIDER EDWARD J, BRENNER Commissioner of Patents A 1 testing Officer 

1. IN A PROCESS FOR THE PRODUCTION OF COLD BY THROTTLING AND WORK-PERFORMING EXPANSION OF A GAS, THE METHOD WHICH COMPRISES COOLING A GAS WHICH HAS BEEN COMPRESSED (1) TO ABOVE CRITICAL PRESSURE AT AMBIENT TEMPERATURE IN A FIRST COOLING STAGE (2), DIVIDING SAID COMPRESSED AND COOLED GAS (13) INTO A FIRST STREAM (16) AND A SECOND STREAM (17), COOLING SAID FIRST AND SAID SECOND STREAMS IN A SECOND COOLING STAGE (4,5) AND IN A FOLLOWING THIRD COOLING STAGE (6), THROTTLING SAID FIRST AND SAID SECOND STREAMS SEPARATELY (7,8) TO BELOW-CRITICAL PRESSURE THERBY LIQUEFYING THEM AT LEAST PARTIALLY, SEPARATING A GASEOUS PART FROM A LIQUID PART (9), WITHDRAWING THE GASEOUS PART (19), HEATING IT BY HEAT-EXCHANGE WITH THE FIRST AND THE SECOND STREAMS IN THE THIRD COOLING STAGE (6), HEATING IT FURTHER BY HEAT-EXCHANGE WITH THE SECOND STREAM IN THE SECOND COOLING STAGE (5), EXPANDING IT BY WORK-PERFORMING EXPANSION (3), HEATING SAID EXPANDED GAS BY HEAT-EXCHANGE WITH THE FIRST STREAM IN THE SECOND COOLING STAGE (4), AND THEN HEATING IT IN SAID FIRST COOLING STAGE (2) BY HEAT-EXCHANGE IN THE COMPRESSED GAS TO AMBIENT TEMPERATURE. 